Primate stem transplantation core. The Primate Stem Cell Transplantation Core will provide three major functions for the investigators of the UW/FHCRC PEGT and for NHLBI investigators. 1) The Core will provide hematopoietic progenitor and stem cell populations from non- human primates, baboons (Papio cynocephalus sp.) and pig-tailed macaques (Macaca nemistrina), for in vitro gene transfer experiments. 2) It will undertake the conduct of in vivo transplantation experiments with gene modified marrow-repopulating cells purified from mobilized blood and/or primed marrow. 3) It will undertake the conduct of studies to test noel tem/progenitor cell mobilization schemes to be used for stem cell gene therapy. Access to large animal transplant models for hematopoietic stem cell gene therapy can be a limiting factor when investigators try to extrapolate findings form the mouse and other small animal models to the human clinical setting. The Primate Stem Cell Transplant Core will function to address these limitations. The Core will be available to all PET supported investigators as well as other NHLBI researchers. In collaboration with the Cell Procurement and Processing Core, specific blood and marrow populations from baboons and macaque species will be provided to investigators for in vitro studies. Importantly, the Core will take advantage of activities in stem cell transplantation and gene transfer in baboons that already exist at the UW-Regional Primate Research Center and FHCRC. The Core not only will provide the care and management of transplanted animals but also will provide expertise on in vitro studies of hematopoiesis, performing transductions, analyzing cells from animals post-transplant and protocol development. To optimize the use of available animals, competitive repopulating strategies will be used to allow direct intra-animal comparisons of different protocols and vectors. The ability of this Core to provide collaborating investigators with a relevant large animal model should greatly facilitate advances in stem cell biology and the eventual application of hematopoietic stem cell gene therapy to the clinical setting.